JP6876337B2 - Nitride semiconductor substrate and its manufacturing method and semiconductor device - Google Patents
Nitride semiconductor substrate and its manufacturing method and semiconductor device Download PDFInfo
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- JP6876337B2 JP6876337B2 JP2018552571A JP2018552571A JP6876337B2 JP 6876337 B2 JP6876337 B2 JP 6876337B2 JP 2018552571 A JP2018552571 A JP 2018552571A JP 2018552571 A JP2018552571 A JP 2018552571A JP 6876337 B2 JP6876337 B2 JP 6876337B2
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- nitride semiconductor
- nitride
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- 150000004767 nitrides Chemical class 0.000 title claims description 287
- 239000004065 semiconductor Substances 0.000 title claims description 249
- 239000000758 substrate Substances 0.000 title claims description 185
- 238000004519 manufacturing process Methods 0.000 title claims description 46
- 239000000463 material Substances 0.000 claims description 71
- 238000000034 method Methods 0.000 claims description 47
- 229910052594 sapphire Inorganic materials 0.000 claims description 37
- 239000010980 sapphire Substances 0.000 claims description 37
- 229910052761 rare earth metal Inorganic materials 0.000 claims description 31
- 239000013078 crystal Substances 0.000 claims description 26
- 150000002910 rare earth metals Chemical class 0.000 claims description 15
- 238000006243 chemical reaction Methods 0.000 claims description 9
- 238000003475 lamination Methods 0.000 claims description 7
- 238000010030 laminating Methods 0.000 claims description 6
- 229910052733 gallium Inorganic materials 0.000 claims description 5
- 229910052751 metal Inorganic materials 0.000 claims description 5
- 239000002184 metal Substances 0.000 claims description 5
- 239000012808 vapor phase Substances 0.000 claims description 5
- 229910052738 indium Inorganic materials 0.000 claims description 4
- 230000008569 process Effects 0.000 claims description 4
- 239000010410 layer Substances 0.000 description 187
- 229910002601 GaN Inorganic materials 0.000 description 100
- JMASRVWKEDWRBT-UHFFFAOYSA-N Gallium nitride Chemical compound [Ga]#N JMASRVWKEDWRBT-UHFFFAOYSA-N 0.000 description 66
- 238000000089 atomic force micrograph Methods 0.000 description 10
- 238000003917 TEM image Methods 0.000 description 7
- 238000002474 experimental method Methods 0.000 description 7
- 230000000694 effects Effects 0.000 description 6
- 230000015572 biosynthetic process Effects 0.000 description 5
- 238000011156 evaluation Methods 0.000 description 5
- 238000002488 metal-organic chemical vapour deposition Methods 0.000 description 5
- -1 GaN Chemical class 0.000 description 4
- 230000007423 decrease Effects 0.000 description 4
- 239000002994 raw material Substances 0.000 description 4
- 230000000149 penetrating effect Effects 0.000 description 3
- 229910002704 AlGaN Inorganic materials 0.000 description 2
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 2
- 239000000654 additive Substances 0.000 description 2
- 230000000996 additive effect Effects 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 229910052747 lanthanoid Inorganic materials 0.000 description 2
- 150000002602 lanthanoids Chemical class 0.000 description 2
- 230000000644 propagated effect Effects 0.000 description 2
- 230000009467 reduction Effects 0.000 description 2
- XCZXGTMEAKBVPV-UHFFFAOYSA-N trimethylgallium Chemical compound C[Ga](C)C XCZXGTMEAKBVPV-UHFFFAOYSA-N 0.000 description 2
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- 229910004298 SiO 2 Inorganic materials 0.000 description 1
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- 229910021529 ammonia Inorganic materials 0.000 description 1
- 229910021417 amorphous silicon Inorganic materials 0.000 description 1
- 230000004888 barrier function Effects 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 239000012159 carrier gas Substances 0.000 description 1
- 238000005229 chemical vapour deposition Methods 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 230000008034 disappearance Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000000407 epitaxy Methods 0.000 description 1
- 230000017525 heat dissipation Effects 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 239000004973 liquid crystal related substance Substances 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 230000010355 oscillation Effects 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 230000008707 rearrangement Effects 0.000 description 1
- 229910052706 scandium Inorganic materials 0.000 description 1
- 238000005389 semiconductor device fabrication Methods 0.000 description 1
- 239000002344 surface layer Substances 0.000 description 1
- 239000010409 thin film Substances 0.000 description 1
- 230000007704 transition Effects 0.000 description 1
- 238000001947 vapour-phase growth Methods 0.000 description 1
- 229910052727 yttrium Inorganic materials 0.000 description 1
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Description
本発明は、表面の転位密度が低減された窒化物半導体基板とその製造方法、および前記窒化物半導体基板を用いて作製された半導体デバイスに関する。 The present invention relates to a nitride semiconductor substrate having a reduced dislocation density on the surface, a method for producing the same, and a semiconductor device manufactured by using the nitride semiconductor substrate.
近年、発光ダイオード（ＬＥＤ：Ｌｉｇｈｔ Ｅｍｉｔｔｉｎｇ Ｄｉｏｄｅ）やレーザダイオード（ＬＤ：Ｌａｓｅｒ Ｄｉｏｄｅ）等の発光デバイスが広く用いられるようになっている。例えばＬＥＤは、各種表示デバイス、携帯電話を始め液晶ディスプレイのバックライト、白色照明等に用いられ、一方、ＬＤは、ブルーレイディスク用光源としてハイビジョン映像の録画再生、光通信、ＣＤ、ＤＶＤ等に用いられている。 In recent years, light emitting devices such as light emitting diodes (LEDs: Light Emitting Diodes) and laser diodes (LDs: Laser Diodes) have come into widespread use. For example, LEDs are used for various display devices, backlights for liquid crystal displays such as mobile phones, white lighting, etc., while LDs are used as light sources for Blu-ray discs for recording and playback of high-definition video, optical communication, CDs, DVDs, etc. Has been done.
また、最近では、携帯電話用ＭＭＩＣ（ｍｏｎｏｌｉｔｈｉｃ ｍｉｃｒｏｗａｖｅ ｉｎｔｅｇｒａｔｅｄ ｃｉｒｃｕｉｔ：モノリシックマイクロ波集積回路）、ＨＥＭＴ（Ｈｉｇｈ Ｅｌｅｃｔｒｏｎ Ｍｏｂｉｌｉｔｙ Ｔｒａｎｓｉｓｔｏｒ：高電子移動度トランジスタ）等の高周波デバイスや、自動車関連向けのインバーター用パワートランジスタ、ショットキーバリアダイオード（ＳＢＤ）等の高出力デバイスの用途が拡大している。 Recently, high-frequency devices such as MMICs (monolithic microwave integrated circuits) for mobile phones, HEMTs (High Electron Mobility Transistors), power transistors for automobiles, inverters for automobiles, etc. Applications of high power devices such as Schottky barrier diodes (SBDs) are expanding.
これらのデバイスを構成する半導体素子は、窒化ガリウム（ＧａＮ）等の窒化物半導体層が形成された窒化物半導体基板を用いて作製されている。このような窒化物半導体基板としては、バルク状単結晶窒化物から切り出されて直接作製された窒化物半導体バルク基板、サファイア等の基材上に単結晶窒化物を成長させた後に基材を除去することにより作製された（擬似的）窒化物半導体バルク基板、基材上に単結晶窒化物を成長させ基材を残したままテンプレートとして半導体デバイスの製造に用いられる窒化物半導体基板がある。 The semiconductor elements constituting these devices are manufactured by using a nitride semiconductor substrate on which a nitride semiconductor layer such as gallium nitride (GaN) is formed. As such a nitride semiconductor substrate, the substrate is removed after the single crystal nitride is grown on a substrate such as a nitride semiconductor bulk substrate or sapphire directly produced by cutting out from a bulk single crystal nitride. There are (pseudo) nitride semiconductor bulk substrates produced by the above, and nitride semiconductor substrates used for manufacturing semiconductor devices as templates while growing single crystal nitrides on the substrate and leaving the substrate.
そして、このような窒化物半導体基板においては、ＬＥＤの内部量子効率やＬＤの発振性能等の特性や、寿命が窒化物半導体基板の表面の転位密度（ＴＤＤ：Ｔｈｒｅａｄｉｎｇ ｄｉｓｌｏｃａｔｉｏｎ ｄｅｎｓｉｔｙ）と関係していることが分かっており、高品質、長寿命の半導体デバイス、特に、上記した高周波デバイスや高出力デバイスでは、転位密度１０６ｃｍ−２オーダー以下の窒化物半導体基板が必要とされている（非特許文献１）。In such a nitride semiconductor substrate, characteristics such as the internal quantum efficiency of the LED and the oscillation performance of the LD, and the lifetime are related to the dislocation density (TDD: Sharing dislocation density) on the surface of the nitride semiconductor substrate. it has been found, high-quality, long-life semiconductor devices, particularly, in high frequency devices and high-power devices described above, the following nitride semiconductor
このように転位密度が低い窒化物半導体基板は、上記した窒化物半導体バルク基板を直接作製する方法により得ることができるが、その工程は複雑であり多大なコストが掛かるため、サファイア基材を用いて窒化物半導体基板を作製する場合に比べて５０〜６０倍高い価格となっている。このため、安価なサファイア基材等を用いて、低転位密度の窒化物半導体基板を安価に提供することができる窒化物半導体基板の製造技術が強く求められている。 A nitride semiconductor substrate having such a low dislocation density can be obtained by the method of directly manufacturing the above-mentioned nitride semiconductor bulk substrate, but the process is complicated and enormous cost is required, so a sapphire substrate is used. The price is 50 to 60 times higher than that of manufacturing a nitride semiconductor substrate. Therefore, there is a strong demand for a technique for manufacturing a nitride semiconductor substrate that can inexpensively provide a nitride semiconductor substrate having a low dislocation density by using an inexpensive sapphire base material or the like.
しかし、サファイア等の基材上に、有機金属気相成長法（ＭＯＣＶＤ：Ｍｅｔａｌ−ｏｒｇａｎｉｃ ｃｈｅｍｉｃａｌ ｖａｐｏｒ ｄｅｐｏｓｉｔｉｏｎ）等を用いて窒化物半導体薄膜を形成させることにより窒化物半導体基板を作製した場合、得られた窒化物半導体基板の転位密度は１０８〜１０１０ｃｍ−２オーダーになり、得られた窒化物半導体基板では設計通りの特性および寿命が得られないことが知られている。However, it is obtained when a nitride semiconductor substrate is produced by forming a nitride semiconductor thin film on a substrate such as sapphire by using a metal-organic chemical vapor deposition (MOCVD) or the like. It is known that the transition density of the nitride semiconductor substrate is on the order of 10 8 to 10 10 cm- 2 , and the obtained nitride semiconductor substrate does not have the characteristics and life as designed.
転位密度を低減する方法としては、ＧａＮ等の窒化物半導体層の厚みを厚くすることが考えられるが、サファイア等の基材とＧａＮ等の窒化物とでは熱膨張係数に差があるため、窒化物半導体層の厚みを厚くした場合には基材との界面に反りが発生するという問題がある。 As a method of reducing the dislocation density, it is conceivable to increase the thickness of the nitride semiconductor layer such as GaN. However, since there is a difference in thermal expansion coefficient between the base material such as sapphire and the nitride such as GaN, nitrided. When the thickness of the physical semiconductor layer is increased, there is a problem that the interface with the base material is warped.
そこで、サファイア等の基材を用いて転位密度が低減された窒化物半導体層を形成させる方法として、サファイア基材上に窒化物のバッファー層を形成した後、非晶質の酸化珪素（ａ−ＳｉＯ２）を用いて選択成長（ＳＡＧ：ｓｅｌｅｃｔｉｖｅ ａｒｅａ ｇｒｏｗｔｈ）マスクを形成し、選択成長マスク上に窒化物半導体層をラテラルエピタキシする方法（ＥＬＯＧ：ｅｐｉｔａｘｉａｌ ｌａｔｅｒａｌ ｏｖｅｒｇｒｏｗｔｈ：エピタキシャル横方向被覆成長法）により、エピタキシ層で転位密度を１０６〜１０７ｃｍ−２オーダーに低減させることが提案されている（特許文献１、２）。Therefore, as a method of forming a nitride semiconductor layer having a reduced dislocation density using a substrate such as sapphire, an amorphous silicon oxide (a-) is formed after forming a nitride buffer layer on the sapphire substrate. By a method of forming a selective growth (SAG: selective area growth) mask using SiO 2 ) and laterally epitaxing the nitride semiconductor layer on the selective growth mask (ELOG: epitaxial lateral cover growth method). It has been proposed to reduce the dislocation density to the order of 10 6 to 10 7 cm- 2 in the epitaxy layer (
しかし、この方法は、選択成長マスクの形成に際して基材を成長装置から取り出して行う必要があり、工程が複雑化し生産効率が低下する。また、低転位密度の領域は選択成長マスクのパターンにより形成されるものであるため、低転位密度の領域が基材上に点在することになり大面積化を図ることができず、窒化物半導体基板の大型化を図ることが難しい。 However, in this method, it is necessary to take out the base material from the growth apparatus when forming the selective growth mask, which complicates the process and lowers the production efficiency. Further, since the low dislocation density region is formed by the pattern of the selective growth mask, the low dislocation density region is scattered on the substrate, and the area cannot be increased, so that the nitride is nitrided. It is difficult to increase the size of the semiconductor substrate.
本発明は、サファイア等の安価な基材上であっても、十分に転位密度が低減された窒化物半導体基板を大面積で製造することができる窒化物半導体基板の製造技術を提供することを課題とする。 The present invention provides a technique for manufacturing a nitride semiconductor substrate capable of manufacturing a nitride semiconductor substrate having a sufficiently reduced dislocation density in a large area even on an inexpensive substrate such as sapphire. Make it an issue.
前記したように、サファイア基材を用いて、高性能、長寿命の半導体デバイスを作製するためには、表面の転位密度が低く制御された窒化物半導体基板を製造する必要があるが、ＥＬＯＧ法では大面積化を図ることができず、窒化物半導体基板の大型化を図ることが難しい。 As described above, in order to manufacture a high-performance, long-life semiconductor device using a sapphire substrate, it is necessary to manufacture a nitride semiconductor substrate in which the dislocation density on the surface is controlled to be low. However, it is difficult to increase the size of the nitride semiconductor substrate.
本発明者は、Ｅｕが添加されたＧａＮ（Ｅｕ添加ＧａＮ層）を発光層とする赤色発光ダイオードの作製に世界に先駆けて成功しているが、その過程において、サファイア基材上に、ドーピング材料が添加されていないアンドープＧａＮ層（ｕｄ−ＧａＮ層）、ドーピング材料としてＥｕが添加されたＧａＮ層（Ｅｕ添加ＧａＮ層）の順に積層して多層化された窒化物半導体層では、転位密度が低下していることを見出した。 The present inventor has succeeded for the first time in the world in producing a red light emitting diode using an Eu-added GaN (Eu-added GaN layer) as a light emitting layer, and in the process, a doping material is placed on a sapphire substrate. The dislocation density is reduced in the nitride semiconductor layer in which the undoped GaN layer (ud-GaN layer) to which is not added and the GaN layer to which Eu is added as the doping material (Eu-added GaN layer) are laminated in this order to form multiple layers. I found that I was doing it.
この知見に基づき、本発明者は、このような積層構造を窒化物半導体基板に適用することができれば、転位密度を十分に低下させて、高性能、長寿命の半導体デバイスの作製が可能になると考え、種々の実験と検討を行った。 Based on this finding, the present inventor believes that if such a laminated structure can be applied to a nitride semiconductor substrate, the dislocation density can be sufficiently reduced and a high-performance, long-life semiconductor device can be manufactured. We thought about it and conducted various experiments and studies.
その結果、このような積層構造を採用した場合、Ｅｕ添加ＧａＮ層におけるＥｕ添加量が１原子％程度、具体的には、０．０１〜２原子％という不純物レベルともいえる少量であっても、劇的に転位密度が低下して、１０６ｃｍ−２オーダー以下の転位密度という高性能、長寿命の半導体デバイスの作製に好適な低転位密度の窒化物半導体基板が得られるという驚くべき結果を得た。As a result, when such a laminated structure is adopted, even if the amount of Eu added in the Eu-added GaN layer is as small as about 1 atomic%, specifically, 0.01 to 2 atomic%, which can be said to be an impurity level. dramatically dislocation density is lowered, 10 6 cm -2 order performance of less dislocation density, the surprising result that the nitride semiconductor substrate of suitable low dislocation density semiconductor device fabrication of long life can be obtained Obtained.
具体的には、積層構造とすることにより、サファイア基材からの貫通転位がＥｕ添加ＧａＮ層を通過する際にその方向が曲げられて表面まで達することがなくなり、サファイア基材上に作製された窒化物半導体基板でありながらも、転位密度が劇的に低下することを見出した。 Specifically, by adopting a laminated structure, when the penetrating dislocations from the sapphire base material pass through the Eu-added GaN layer, the direction is not bent and reaches the surface, and the dislocations are formed on the sapphire base material. It was found that the dislocation density is dramatically reduced even though it is a nitride semiconductor substrate.
そして、ｕｄ−ＧａＮ層とＥｕ添加ＧａＮ層との好ましい積層方法について、さらに、実験と検討を進めたところ、以下の知見を得た。 Then, as a result of further experiments and studies on a preferable lamination method of the ud-GaN layer and the Eu-added GaN layer, the following findings were obtained.
即ち、積層回数を１回とする場合には、ｕｄ−ＧａＮ層の上に積層されるＥｕ添加ＧａＮ層の厚みの増加に比例して転位密度が低下し、総厚が３μｍ以下という薄さでありながら、十分に転位密度が低下した窒化物半導体基板を提供することができることを見出した。 That is, when the number of laminations is one, the dislocation density decreases in proportion to the increase in the thickness of the Eu-added GaN layer laminated on the ud-GaN layer, and the total thickness is as thin as 3 μm or less. However, they have found that it is possible to provide a nitride semiconductor substrate having a sufficiently reduced dislocation density.
一方、積層回数を複数回にして、窒化物半導体層を超格子構造の窒化物半導体層とした場合には、Ｅｕ添加ＧａＮ層の厚みがｕｄ−ＧａＮ層厚みの１／１０程度であっても、積層回数の増加に比例して転位密度が低下することを見出した。そして、このような超格子構造とすることにより、総厚が３μｍ以下という薄さでありながら、十分に転位密度が低下した窒化物半導体基板を提供することができることが分かった。 On the other hand, when the number of laminations is multiple and the nitride semiconductor layer is a nitride semiconductor layer having a superlattice structure, even if the thickness of the Eu-added GaN layer is about 1/10 of the thickness of the ud-GaN layer. , It was found that the dislocation density decreases in proportion to the increase in the number of laminations. Then, it was found that by adopting such a superlattice structure, it is possible to provide a nitride semiconductor substrate having a total thickness of 3 μm or less and a sufficiently reduced dislocation density.
そして、ｕｄ−ＧａＮ層とＥｕ添加ＧａＮ層との積層は、ＥＬＯＧ法と異なり、サファイア基材上の全面で行うことができるため、窒化物半導体層の大面積化を実現することができ、窒化物半導体基板の大型化を図ることができる。 Unlike the ELOG method, the ud-GaN layer and the Eu-added GaN layer can be laminated on the entire surface of the sapphire substrate, so that the area of the nitride semiconductor layer can be increased and nitrided. The size of the physical semiconductor substrate can be increased.
なお、このような積層構造を形成させることによってサファイア基材からの貫通転位がＥｕ添加ＧａＮ層において曲げられて表面まで達することがなくなり、転位密度が低下した理由としては、以下のように推測される。 By forming such a laminated structure, the penetrating dislocations from the sapphire substrate are not bent in the Eu-added GaN layer and reach the surface, and the reason why the dislocation density is lowered is presumed as follows. To.
即ち、Ｅｕ添加ＧａＮ層においては、ＥｕがＧａと置換する形で導入されるが、Ｅｕの原子半径はＧａに比べて約１．５倍大きいために、Ｇａと置換されたＥｕの周囲に歪が生じて、非晶質部分が形成される。その結果、貫通転位等の転位はＥｕ添加ＧａＮ層で直線的に伝播されなくなり、表面の転位密度が低下したと推測される。 That is, in the Eu-added GaN layer, Eu is introduced in a form of replacing Ga, but since the atomic radius of Eu is about 1.5 times larger than that of Ga, it is distorted around the Eu replaced with Ga. Is generated, and an amorphous portion is formed. As a result, it is presumed that dislocations such as through dislocations are not linearly propagated in the Eu-added GaN layer, and the dislocation density on the surface is lowered.
上記においては、窒化物としてＧａＮ、添加元素としてＥｕを挙げて説明したが、窒化物としては、ＧａＮ以外のＡｌＮ、ＩｎＮ等のいわゆるＧａＮ系の窒化物（ＩｎＧａＮやＡｌＧａＮ等の混晶を含む）であっても同様に扱うことができる。そして、添加元素としてはＥｕに限定されず、Ｓｃ、Ｙ、およびＬａからＬｕまでのランタノイド系元素を総称した希土類元素であれば、同様に転位密度が十分に低下した窒化物半導体基板を提供することができる。 In the above description, GaN is used as the nitride and Eu is used as the additive element, but as the nitride, so-called GaN-based nitrides such as AlN and InN other than GaN (including mixed crystals such as InGaN and AlGaN) are used. However, it can be treated in the same way. The additive element is not limited to Eu, and if it is a rare earth element that collectively refers to Sc, Y, and lanthanoid elements from La to Lu, a nitride semiconductor substrate having a sufficiently reduced rearrangement density is similarly provided. be able to.
また、基材としては、サファイアの他に、ＳｉＣやＳｉを用いてもよく、また、厚みの薄いＧａＮを基材として用いてもよい。ＳｉＣは安価であり、かつ熱伝導性が高く放熱性に優れているため、高パワーの半導体デバイス製造に好適な窒化物半導体基板を安価に提供することができる。そして、Ｓｉは大きなサイズの基材を容易に入手することが可能であるため、大型化された窒化物半導体基板を提供することができる。また、厚みの薄いＧａＮを基材として用いることにより、ＧａＮバルク基板を安価に提供することができる。 Further, as the base material, in addition to sapphire, SiC or Si may be used, or GaN having a thin thickness may be used as the base material. Since SiC is inexpensive, has high thermal conductivity, and is excellent in heat dissipation, it is possible to inexpensively provide a nitride semiconductor substrate suitable for manufacturing a high-power semiconductor device. Since Si can easily obtain a large-sized base material, it is possible to provide a large-sized nitride semiconductor substrate. Further, by using GaN having a thin thickness as a base material, a GaN bulk substrate can be provided at low cost.
以上のように、本技術によれば、基材上に窒化物半導体層が形成された窒化物半導体基板において、窒化物半導体層を局所的な歪が異なる２以上の窒化物層を用いて交互に積層された構造に形成することにより、基材側からの転位の少なくとも一部が曲げられて、表面に到達するまでに消滅させることができる。その結果、窒化物半導体層の表面における転位密度が、高性能、長寿命の半導体デバイスの作製に好適とされる１０６ｃｍ−２オーダー以下にまで低下した窒化物半導体基板を提供することができる。As described above, according to the present technology, in a nitride semiconductor substrate in which a nitride semiconductor layer is formed on a base material, the nitride semiconductor layers are alternately used by using two or more nitride layers having different local strains. By forming the structure laminated on the substrate, at least a part of the dislocations from the substrate side can be bent and disappear by the time it reaches the surface. As a result, it is possible to provide the dislocation density on the surface of the nitride semiconductor layer, a high performance, a nitride semiconductor substrate was reduced to 10 6 cm -2 order below are suitable for manufacturing a semiconductor device of long life ..
また、基材上に形成された窒化物半導体層を基材から取り外すことにより、取り外された窒化物半導体層を窒化物半導体バルク基板として用いることができる。 Further, by removing the nitride semiconductor layer formed on the base material from the base material, the removed nitride semiconductor layer can be used as the nitride semiconductor bulk substrate.
請求項１〜１４に記載の発明は上記の知見に基づくものであり、請求項１に記載の発明は、
基材上に窒化物半導体層が形成された窒化物半導体基板であって、
前記窒化物半導体層が、
ドーピング材料が添加されていない厚み０．１〜５０ｎｍのアンドープ窒化物層と、
ドーピング材料として希土類元素が添加された厚み０．１〜２０００ｎｍの希土類元素添加窒化物層とが１回積層されて形成されており、
前記窒化物半導体層の表面における転位密度が１０６ｃｍ−２オーダー以下であることを特徴とする窒化物半導体基板である。The inventions according to
A nitride semiconductor substrate in which a nitride semiconductor layer is formed on a base material.
The nitride semiconductor layer
An undoped nitride layer with a thickness of 0.1 to 50 nm to which no doping material is added,
A rare earth element-added nitride layer having a thickness of 0.1 to 2000 nm to which a rare earth element is added as a doping material is laminated once and formed.
A nitride semiconductor substrate, wherein the dislocation density on the surface of the nitride semiconductor layer is not more than 10 6 cm -2 order.
そして、請求項２に記載の発明は、
基材上に窒化物半導体層が形成された窒化物半導体基板であって、
前記窒化物半導体層が、
ドーピング材料が添加されていない厚み０．１〜５０ｎｍのアンドープ窒化物層と、
ドーピング材料として希土類元素が添加された厚み０．１〜２００ｎｍの希土類元素添加窒化物層とが複数回積層されて超格子構造に形成されており、
前記窒化物半導体層の表面における転位密度が１０６ｃｍ−２オーダー以下であることを特徴とする窒化物半導体基板である。The invention according to
A nitride semiconductor substrate in which a nitride semiconductor layer is formed on a base material.
The nitride semiconductor layer
An undoped nitride layer with a thickness of 0.1 to 50 nm to which no doping material is added,
A rare earth element-added nitride layer having a thickness of 0.1 to 200 nm added as a doping material is laminated multiple times to form a superlattice structure.
A nitride semiconductor substrate, wherein the dislocation density on the surface of the nitride semiconductor layer is not more than 10 6 cm -2 order.
また、請求項３に記載の発明は、
積層回数が２〜３００回であることを特徴とする請求項２に記載の窒化物半導体基板である。Further, the invention according to claim 3 is
The nitride semiconductor substrate according to
また、請求項４に記載の発明は、
前記窒化物半導体層における窒化物が、ＧａＮ、ＩｎＮ、ＡｌＮ、またはこれらのいずれか２つ以上の混晶であることを特徴とする請求項１ないし請求項３のいずれか１項に記載の窒化物半導体基板である。Further, the invention according to claim 4 is
The nitride according to any one of
また、請求項５に記載の発明は、
前記希土類元素が、Ｅｕであることを特徴とする請求項１ないし請求項４のいずれか１項に記載の窒化物半導体基板である。Further, the invention according to claim 5 is
The nitride semiconductor substrate according to any one of
また、請求項６に記載の発明は、
前記Ｅｕの添加量が、０．０１〜２原子％であることを特徴とする請求項５に記載の窒化物半導体基板である。Further, the invention according to claim 6 is
The nitride semiconductor substrate according to claim 5, wherein the amount of Eu added is 0.01 to 2 atomic%.
また、請求項７に記載の発明は、
総厚が３μｍ以下であることを特徴とする請求項１ないし請求項６のいずれか１項に記載の窒化物半導体基板である。Further, the invention according to claim 7 is
The nitride semiconductor substrate according to any one of
また、請求項８に記載の発明は、
前記基材がサファイア、ＳｉＣ、Ｓｉ、ＧａＮのいずれかであることを特徴とする請求項１ないし請求項７のいずれか１項に記載の窒化物半導体基板である。Further, the invention according to claim 8 is
The nitride semiconductor substrate according to any one of
また、請求項９に記載の発明は、
基材上に窒化物半導体層が形成された窒化物半導体基板であって、
前記窒化物半導体層が、局所的な歪が異なる厚み０．１〜５０ｎｍのアンドープ窒化物層および厚み０．１〜２０００ｎｍの希土類元素添加窒化物層が交互に１回積層された構造を有しており、
前記窒化物半導体層の表面における転位密度が１０６ｃｍ−２オーダー以下であることを特徴とする窒化物半導体基板である。Further, the invention according to claim 9 is
A nitride semiconductor substrate in which a nitride semiconductor layer is formed on a base material.
The nitride semiconductor layer has a structure in which an undoped nitride layer having a thickness of 0.1 to 50 nm and a rare earth element-added nitride layer having a thickness of 0.1 to 2000 nm having different local strains are alternately laminated once. And
A nitride semiconductor substrate, wherein the dislocation density on the surface of the nitride semiconductor layer is not more than 10 6 cm -2 order.
また、請求項１０に記載の発明は、
基材上に窒化物半導体層が形成された窒化物半導体基板であって、
前記窒化物半導体層が、局所的な歪が異なる厚み０．１〜５０ｎｍのアンドープ窒化物層および厚み０．１〜２００ｎｍの希土類元素添加窒化物層が交互に複数回積層された超格子構造を有しており、
前記窒化物半導体層の表面における転位密度が１０６ｃｍ−２オーダー以下であることを特徴とする窒化物半導体基板である。Further, the invention according to
A nitride semiconductor substrate in which a nitride semiconductor layer is formed on a base material.
The nitride semiconductor layer has a superlattice structure in which an undoped nitride layer having a thickness of 0.1 to 50 nm and a rare earth element-added nitride layer having a thickness of 0.1 to 200 nm having different local strains are alternately laminated a plurality of times. Have and
A nitride semiconductor substrate, wherein the dislocation density on the surface of the nitride semiconductor layer is not more than 10 6 cm -2 order.
また、請求項１１に記載の発明は、
基材側からの転位の少なくとも一部が、前記窒化物半導体層の前記交互に積層された構造において曲げられて、表面に到達するまでに消滅していることを特徴とする請求項９または請求項１０に記載の窒化物半導体基板である。Further, the invention according to claim 11
9. Or claim, wherein at least a part of the dislocations from the substrate side is bent in the alternately laminated structure of the nitride semiconductor layer and disappears by the time it reaches the surface.
また、請求項１２に記載の発明は、
前記窒化物半導体層が、前記基材から取り外されて窒化物半導体バルク基板として形成されていることを特徴とする請求項９ないし請求項１１のいずれか１項に記載の窒化物半導体基板である。Further, the invention according to claim 12
The nitride semiconductor substrate according to any one of claims 9 to 11, wherein the nitride semiconductor layer is removed from the base material to form a nitride semiconductor bulk substrate. ..
そして、上記した本発明に係る窒化物半導体基板は、十分に転位密度が低下した窒化物半導体基板であるため、発光デバイスだけでなく、高周波デバイスや高出力デバイスにも好適に使用することができる。 Since the nitride semiconductor substrate according to the present invention described above is a nitride semiconductor substrate having a sufficiently reduced dislocation density, it can be suitably used not only for light emitting devices but also for high frequency devices and high output devices. ..
即ち、請求項１３に記載の発明は、
請求項１ないし請求項１２のいずれか１項に記載の窒化物半導体基板を用いて作製されていることを特徴とする半導体デバイスである。That is, the invention according to claim 13 is
A semiconductor device characterized in that it is manufactured by using the nitride semiconductor substrate according to any one of
また、請求項１４に記載の発明は、
発光デバイス、高周波デバイス、高出力デバイスのいずれかであることを特徴とする請求項１３に記載の半導体デバイスである。Further, the invention according to claim 14
The semiconductor device according to claim 13, wherein the semiconductor device is any of a light emitting device, a high frequency device, and a high output device.
上記した本発明に係る窒化物半導体基板は、有機金属気相エピタキシャル法（ＯＭＶＰＥ法）を用いて、９００〜１２００℃の温度条件で、途中で反応容器から取り出すことなく一連の工程で、ドーピング材料が添加されていないアンドープ窒化物層と、ドーピング材料としてＥｕなどの希土類元素が添加された希土類元素添加窒化物層とを、サファイア等の基材上に積層させることにより製造することができる。 The above-mentioned nitride semiconductor substrate according to the present invention is a doping material using an organic metal vapor phase epitaxial method (OMVPE method) in a series of steps under temperature conditions of 900 to 1200 ° C. without taking it out of the reaction vessel in the middle. It can be produced by laminating an undoped nitride layer to which is not added and a rare earth element-added nitride layer to which a rare earth element such as Eu is added as a doping material on a substrate such as sapphire.
窒化物層の成長に際して、その成長温度を高くすると、表面まで貫通した転位によるピット（穴）が大きくなり、転位密度を十分に低減させることができない。一方、温度を低くすると、ピットが小さくなり転位密度を十分に低減させることができる。 When the growth temperature of the nitride layer is raised, the pits (holes) due to dislocations penetrating to the surface become large, and the dislocation density cannot be sufficiently reduced. On the other hand, when the temperature is lowered, the pits become smaller and the dislocation density can be sufficiently reduced.
このため、本発明においては、窒化物層の成長温度を９００〜１１００℃に設定する。このような温度条件とすることにより、希土類元素添加窒化物層を通過して表面まで達した転位によるピットを小さくさせることができ、さらに、Ｅｕなどの希土類元素を窒化物を構成するＧａやＡｌ、Ｉｎと確実に置換させて添加することができるため、十分に転位密度を低下させた窒化物半導体基板を製造することができる。 Therefore, in the present invention, the growth temperature of the nitride layer is set to 900 to 1100 ° C. By setting such a temperature condition, it is possible to reduce the pits due to dislocations that have passed through the rare earth element-added nitride layer and reached the surface, and further, rare earth elements such as Eu can be used as Ga or Al to form the nitride. , In can be reliably substituted and added, so that a nitride semiconductor substrate having a sufficiently reduced dislocation density can be manufactured.
そして、アンドープ窒化物層と希土類元素添加窒化物層の形成は、ＧａＮ結晶の成長に際してＥｕなどを添加するか否かで行うことができるため、反応容器から取り出すことなく一連の工程で行うことができ、高い生産効率で、大型化された窒化物半導体基板を安価に製造することができる。 Since the undoped nitride layer and the rare earth element-added nitride layer can be formed by adding Eu or the like when the GaN crystal grows, it can be performed in a series of steps without taking it out of the reaction vessel. It is possible to inexpensively manufacture a large-sized nitride semiconductor substrate with high production efficiency.
即ち、請求項１５に記載の発明は、
基材上に窒化物半導体層が形成された窒化物半導体基板の製造方法であって、
基材上にＧａＮ、ＩｎＮ、ＡｌＮ、またはこれらのいずれか２つ以上の混晶を成長させて、ドーピング材料が添加されていないアンドープ窒化物層を０．１〜５０ｎｍの厚みに形成する工程と、
前記アンドープ窒化物層の上に、ＧａＮ、ＩｎＮ、ＡｌＮ、またはこれらのいずれか２つ以上の混晶を母体材料とし、ドーピング材料として希土類元素をＧａ、ＩｎあるいはＡｌと置換するように添加することにより、希土類元素添加窒化物層を０．１〜２０００ｎｍの厚みに形成する工程とを備えており、
前記２つの工程を、有機金属気相エピタキシャル法を用いて、９００〜１２００℃の温度条件の下で、反応容器から取り出すことなく一連の形成工程によって行うことを特徴とする窒化物半導体基板の製造方法である。That is, the invention according to claim 15
A method for manufacturing a nitride semiconductor substrate in which a nitride semiconductor layer is formed on a base material.
A step of growing GaN, InN, AlN, or a mixed crystal of any two or more of these on a substrate to form an undoped nitride layer having no doping material added to a thickness of 0.1 to 50 nm. ,
On the undoped nitride layer, GaN, InN, AlN, or a mixed crystal of any two or more of these is used as a base material, and a rare earth element is added as a doping material so as to replace Ga, In, or Al. It is provided with a step of forming a rare earth element-added nitride layer to a thickness of 0.1 to 2000 nm.
Manufacture of a nitride semiconductor substrate, wherein the two steps are carried out by a series of forming steps using an organic metal vapor phase epitaxial method under a temperature condition of 900 to 1200 ° C. without taking out from the reaction vessel. The method.
そして、請求項１６に記載の発明は、
基材上に窒化物半導体層が形成された窒化物半導体基板の製造方法であって、
基材上にＧａＮ、ＩｎＮ、ＡｌＮ、またはこれらのいずれか２つ以上の混晶を成長させて、ドーピング材料が添加されていないアンドープ窒化物層を形成する工程と、
前記アンドープ窒化物層の上に、ＧａＮ、ＩｎＮ、ＡｌＮ、またはこれらのいずれか２つ以上の混晶を母体材料とし、ドーピング材料として希土類元素をＧａ、ＩｎあるいはＡｌと置換するように添加することにより、希土類元素添加窒化物層を０．１〜２００ｎｍの厚みに形成する工程とを備えており、
前記２つの工程を、有機金属気相エピタキシャル法を用いて、９００〜１２００℃の温度条件の下で、反応容器から取り出すことなく一連の形成工程によって、交互に、複数回繰り返し行うことを特徴とする窒化物半導体基板の製造方法である。The invention according to claim 16 is
A method for manufacturing a nitride semiconductor substrate in which a nitride semiconductor layer is formed on a base material.
A step of growing GaN, InN, AlN, or a mixed crystal of any two or more of these on a substrate to form an undoped nitride layer to which no doping material is added.
On the undoped nitride layer, GaN, InN, AlN, or a mixed crystal of any two or more of these is used as a base material, and a rare earth element is added as a doping material so as to replace Ga, In, or Al. It is provided with a step of forming a rare earth element-added nitride layer to a thickness of 0.1 to 200 nm.
The feature is that the above two steps are alternately repeated a plurality of times by a series of forming steps using an organic metal vapor phase epitaxial method under a temperature condition of 900 to 1200 ° C. without taking out from the reaction vessel. This is a method for manufacturing a nitride semiconductor substrate.
前記したように、積層を繰り返して超格子構造の窒化物半導体層とすることにより、総厚が３μｍ以下という薄さでありながら、十分に転位密度が低下した窒化物半導体基板を製造することができる。 As described above, by repeating the lamination to form a nitride semiconductor layer having a superlattice structure, it is possible to manufacture a nitride semiconductor substrate having a total thickness of 3 μm or less and a sufficiently reduced dislocation density. it can.
また、請求項１７に記載の発明は、
前記希土類元素として、Ｅｕを用いることを特徴とする請求項１５または請求項１６に記載の窒化物半導体基板の製造方法である。Further, the invention according to claim 17
The method for producing a nitride semiconductor substrate according to claim 15 or 16, wherein Eu is used as the rare earth element.
Ｅｕは、ランタノイド系の希土類元素の内でも、Ｇａと置換された際、周囲に歪みを生じさせて転位の伝播を抑制するに適切な原子半径を有しているため、効率的に表面の転位密度を低下させることができる。 Even among the rare earth elements of the lanthanoid system, Eu has an atomic radius suitable for causing distortion in the surroundings and suppressing the propagation of dislocations when replaced with Ga, so that dislocations on the surface are efficiently performed. The density can be reduced.
また、Ｅｕは、Ｅｕ化合物の入手が容易であるためドーピング材料として好ましい。 In addition, Eu is preferable as a doping material because the Eu compound is easily available.
また、請求項１８に記載の発明は、
Ｅｕを、Ｅｕ｛Ｎ［Ｓｉ（ＣＨ３）３］２｝３、Ｅｕ（Ｃ１１Ｈ１９Ｏ２）３、Ｅｕ［Ｃ５（ＣＨ３）４（Ｃ３Ｈ７）］２のいずれかにより供給することを特徴とする請求項１７に記載の窒化物半導体基板の製造方法である。Further, the invention according to claim 18
Eu by any of Eu {N [Si (CH 3 ) 3 ] 2 } 3 , Eu (C 11 H 19 O 2 ) 3 , Eu [C 5 (CH 3 ) 4 (C 3 H 7 )] 2. The method for manufacturing a nitride semiconductor substrate according to claim 17, wherein the nitride semiconductor substrate is supplied.
具体的なＥｕ源としては、例えば、Ｅｕ［Ｃ５（ＣＨ３）５］２、Ｅｕ［Ｃ５（ＣＨ３）４Ｈ］２、Ｅｕ｛Ｎ［Ｓｉ（ＣＨ３）３］２｝３、Ｅｕ（Ｃ５Ｈ７Ｏ２）３、Ｅｕ（Ｃ１１Ｈ１９Ｏ２）３、Ｅｕ［Ｃ５（ＣＨ３）４（Ｃ３Ｈ７）］２等を挙げることができるが、これらの内でも、Ｅｕ｛Ｎ［Ｓｉ（ＣＨ３）３］２｝３やＥｕ（Ｃ１１Ｈ１９Ｏ２）３、Ｅｕ［Ｃ５（ＣＨ３）４（Ｃ３Ｈ７）］２は、反応装置内での蒸気圧が高いため、効率的な添加を行うことができる。Specific Eu sources include, for example, Eu [C 5 (CH 3 ) 5 ] 2 , Eu [C 5 (CH 3 ) 4 H] 2 , Eu {N [Si (CH 3 ) 3 ] 2 } 3 , Eu (C 5 H 7 O 2 ) 3 , Eu (C 11 H 19 O 2 ) 3 , Eu [C 5 (CH 3 ) 4 (C 3 H 7 )] 2 and the like can be mentioned. However, Eu {N [Si (CH 3 ) 3 ] 2 } 3 and Eu (C 11 H 19 O 2 ) 3 , Eu [C 5 (CH 3 ) 4 (C 3 H 7 )] 2 are in the reactor. Since the steam pressure is high, efficient addition can be performed.
また、請求項１９に記載の発明は、
前記基材として、サファイア、ＳｉＣ、Ｓｉ、ＧａＮのいずれかを用いることを特徴とする請求項１５ないし請求項１８のいずれか１項に記載の窒化物半導体基板の製造方法である。Further, the invention according to claim 19
The method for manufacturing a nitride semiconductor substrate according to any one of claims 15 to 18, wherein any one of sapphire, SiC, Si, and GaN is used as the base material.
また、請求項２０に記載の発明は、
さらに、基材上に形成された窒化物半導体層を前記基材から取り外して、窒化物半導体バルク基板とする工程を備えていることを特徴とする請求項１５ないし請求項１９のいずれか１項に記載の窒化物半導体基板の製造方法である。Further, the invention according to
Further, any one of claims 15 to 19, further comprising a step of removing the nitride semiconductor layer formed on the base material from the base material to obtain a nitride semiconductor bulk substrate. The method for manufacturing a nitride semiconductor substrate according to the above.
基材上に形成された窒化物半導体層を基材から取り外すことにより、窒化物半導体層を窒化物半導体バルク基板として用いることができる。 By removing the nitride semiconductor layer formed on the base material from the base material, the nitride semiconductor layer can be used as the nitride semiconductor bulk substrate.
本発明によれば、サファイア等の安価な基材上であっても、十分に転位密度が低減された窒化物半導体基板を大面積で製造することができる窒化物半導体基板の製造技術を提供することができる。 According to the present invention, there is provided a technique for manufacturing a nitride semiconductor substrate capable of manufacturing a nitride semiconductor substrate having a sufficiently reduced dislocation density in a large area even on an inexpensive substrate such as sapphire. be able to.
以下、本発明を実施の形態に基づいて説明する。なお、以下においては、基材としてサファイア、窒化物半導体層としてＧａＮ層、添加される希土類元素としてＥｕを例に挙げて説明するが、前記したように、これらに限定されるものではない。 Hereinafter, the present invention will be described based on the embodiments. In the following description, sapphire as a base material, a GaN layer as a nitride semiconductor layer, and Eu as an added rare earth element will be described as examples, but the present invention is not limited to these.
［１］第１の実施の形態
本実施の形態においては、サファイア基材上に、アンドープ窒化物層（ｕｄ−ＧａＮ層）と、希土類元素としてＥｕが添加された希土類元素添加窒化物層（Ｅｕ添加ＧａＮ層）とが１層ずつ積層されて、窒化物半導体層が形成された窒化物半導体基板について説明する。[1] First Embodiment In the present embodiment, an undoped nitride layer (ud-GaN layer) and a rare earth element-added nitride layer (Eu) to which Eu is added as a rare earth element are added on a sapphire substrate. The nitride semiconductor substrate on which the added GaN layer) is laminated one by one to form the nitride semiconductor layer will be described.
１．窒化物半導体基板の基本的な構成
最初に本実施の形態に係る窒化物半導体基板の基本的な構成について説明する。図１は、本実施の形態に係る窒化物半導体基板の構成を示す模式図である。図１において、１は窒化物半導体基板、１０はサファイア基材、２０はｕｄ−ＧａＮ層２１およびＥｕ添加ＧａＮ層２２をペアとして１回積層した窒化物半導体層である。1. 1. Basic Configuration of Nitride Semiconductor Substrate First, the basic configuration of the nitride semiconductor substrate according to the present embodiment will be described. FIG. 1 is a schematic view showing the configuration of a nitride semiconductor substrate according to the present embodiment. In FIG. 1, 1 is a nitride semiconductor substrate, 10 is a sapphire substrate, and 20 is a nitride semiconductor layer in which an ud-
なお、本実施の形態に係る窒化物半導体基板はサファイア基材上に窒化物半導体層を形成させたままテンプレートとして半導体デバイスの製造に用いられる場合もあり、その際、窒化物半導体層はバッファー（ｂｕｆｆｅｒ）層として機能するため、この窒化物半導体層をバッファー（ｂｕｆｆｅｒ）層と表現する場合もある。 The nitride semiconductor substrate according to the present embodiment may be used as a template for manufacturing a semiconductor device with the nitride semiconductor layer formed on the sapphire substrate, and at that time, the nitride semiconductor layer is used as a buffer ( Since it functions as a buffer layer, this nitride semiconductor layer may be referred to as a buffer layer.
そして、本実施の形態においては、図１に示すように、サファイア基材１０と窒化物半導体層２０との間に、サファイア基材１０とＧａＮの格子定数の差（格子不整合）によるクラックの発生を防止するために４７５℃程度で低温成長させたＬＴ−ＧａＮ層３０と、サファイア基材１０と窒化物半導体層（バッファー層）２０との間の距離を大きくして転位の影響を抑制するためのｕｄ−ＧａＮ層４０とを予め形成している。
Then, in the present embodiment, as shown in FIG. 1, cracks between the
２．窒化物半導体基板の製造方法
次に、本実施の形態に係る窒化物半導体基板の製造方法について、厚み１０ｎｍのｕｄ−ＧａＮ層２１および厚み３００ｎｍのＥｕ添加ＧａＮ層２２を積層して窒化物半導体基板１を製造した例を挙げて、具体的に説明する。2. Method for Manufacturing Nitride Semiconductor Substrate Next, regarding the method for manufacturing the nitride semiconductor substrate according to the present embodiment, the ud-
最初に、有機金属気相成長法（ＯＭＶＰＥ法）を用いて、サファイア基材１０上に、成長温度４７５℃、圧力１００ｋＰａの条件下、成長速度１．３μｍ／ｈで厚み約３０ｎｍのＬＴ−ＧａＮ層３０を形成し、その後、ＬＴ−ＧａＮ層３０上に、成長温度１１５０℃、圧力１００ｋＰａの条件下、成長速度０．８μｍ／ｈで厚さ約２μｍのｕｄ−ＧａＮ層４０を形成した。
First, using the metalorganic vapor phase growth method (OMVPE method), LT-GaN having a growth rate of 1.3 μm / h and a thickness of about 30 nm on a
次に、同様にＯＭＶＰＥ法を用いて、ｕｄ−ＧａＮ層４０上に、成長温度９６０℃、圧力１００ｋＰａの条件下、成長速度０．８μｍ／ｈで厚み３００ｎｍのＥｕ添加ＧａＮ層２２を形成した。
Next, similarly, using the OMVPE method, an Eu-added
次に、同様にＯＭＶＰＥ法を用いて、Ｅｕ添加ＧａＮ層２２上に、成長温度９６０℃、圧力１００ｋＰａの条件下、成長速度０．８μｍ／ｈで厚み１０ｎｍのｕｄ−ＧａＮ層２１を形成した。このように、Ｅｕ添加ＧａＮ層２２とｕｄ−ＧａＮ層２１とを１層ずつ積層することにより、窒化物半導体層２０を形成させ、窒化物半導体基板１の製造を完了した。
Next, similarly, using the OMVPE method, an ud-
なお、上記において、Ｇａ原料としてはトリメチルガリウム（ＴＭＧａ）を用い、供給量は０．５５ｓｃｃｍとした。そして、Ｎ原料としてはアンモニア（ＮＨ３）を用い、供給量は４．０ｓｌｍとした。また、Ｅｕ有機原料としてはキャリアガス（水素ガス：Ｈ２）でバブリングしたＥｕ［Ｃ５（ＣＨ３）４（Ｃ３Ｈ７）］２を用い、供給量は１．５ｓｌｍとした（供給温度：１１５℃）。In the above, trimethylgallium (TMGa) was used as the Ga raw material, and the supply amount was 0.55 sccm. Ammonia (NH 3 ) was used as the N raw material, and the supply amount was 4.0 slm. As the Eu organic raw material, Eu [C 5 (CH 3 ) 4 (C 3 H 7 )] 2 bubbled with a carrier gas (hydrogen gas: H 2 ) was used, and the supply amount was 1.5 slm (supply temperature). : 115 ° C).
このとき、ＯＭＶＰＥ装置の配管バルブ等を通常仕様のもの（耐熱温度８０〜１００℃）から高温特殊仕様のものに変更することにより、Ｅｕ原料の供給温度を１１５〜１３５℃の十分高い温度に保って、十分な量のＥｕを反応管に供給できるようにした。
At this time, by changing the piping valve of the OMVPE device from the normal specification (heat
そして、本実施の形態において、各層の形成は、途中で試料を反応管より取り出すことなく、成長の中断がないように一連の工程で行った。 Then, in the present embodiment, the formation of each layer was carried out in a series of steps so that the sample was not taken out from the reaction tube in the middle and the growth was not interrupted.
３．転位密度の評価
（１）ＴＥＭ画像に基づく評価
上記で得られた窒化物半導体基板の表面における転位密度について、まず、透過型電子顕微鏡（ＴＥＭ）を用いて断面を観察して、転位密度の低減効果について評価した。3. 3. Evaluation of dislocation density (1) Evaluation based on TEM image Regarding the dislocation density on the surface of the nitride semiconductor substrate obtained above, first, the cross section is observed using a transmission electron microscope (TEM) to reduce the dislocation density. The effect was evaluated.
図２は、窒化物半導体基板のＴＥＭ画像である。図２より、この窒化物半導体基板においては、最下層のサファイア基材の上に形成されたｕｄ−ＧａＮ層に発生した転位が表面に向けて伝播されていることが分かる。しかし、これらの転位の内、右側の濃色の１点鎖線で丸く囲んだ部分では表面まで転位が到達しているものの、左側の薄色の１点鎖線で丸く囲んだ部分では転位が表面に到達するまでに、ｕｄ−ＧａＮ層とＥｕ添加ＧａＮ層が積層された窒化物半導体層（バッファー層）内で消滅している。この結果より、本実施の形態によれば、窒化物半導体基板において、転位密度を低減できることが確認できる。 FIG. 2 is a TEM image of a nitride semiconductor substrate. From FIG. 2, it can be seen that in this nitride semiconductor substrate, dislocations generated in the ud-GaN layer formed on the lowermost sapphire substrate are propagated toward the surface. However, of these dislocations, the dislocations reach the surface in the part circled by the dark one-dot chain line on the right side, but the dislocations reach the surface in the part circled by the light-colored one-dot chain line on the left side. By the time it reaches, it has disappeared in the nitride semiconductor layer (buffer layer) in which the ud-GaN layer and the Eu-added GaN layer are laminated. From this result, it can be confirmed that the dislocation density can be reduced in the nitride semiconductor substrate according to the present embodiment.
（２）ＡＦＭ画像に基づく評価
次に、窒化物半導体層（バッファー層）の形成の前後において表面に現われた転位の様子を原子間力顕微鏡（ＡＦＭ）により観察して、転位密度の低減効果について評価した。なお、観察は１μｍ四方の同じ箇所で行った。(2) Evaluation based on AFM image Next, the state of dislocations appearing on the surface before and after the formation of the nitride semiconductor layer (buffer layer) is observed with an atomic force microscope (AFM), and the effect of reducing the dislocation density is observed. evaluated. The observation was performed at the
図３は窒化物半導体基板の表面のＡＦＭ画像であり、（ａ）は窒化物半導体層（バッファー層）形成前のｕｄ−ＧａＮ層の表面、（ｂ）窒化物半導体層（バッファー層）形成後の窒化物半導体層（バッファー層）の表面を示している。 FIG. 3 is an AFM image of the surface of the nitride semiconductor substrate, (a) is the surface of the ud-GaN layer before the nitride semiconductor layer (buffer layer) is formed, and (b) is after the nitride semiconductor layer (buffer layer) is formed. The surface of the nitride semiconductor layer (buffer layer) is shown.
図３（ａ）に示すように、ｕｄ−ＧａＮ層の表面では、丸で囲んだ多くの箇所に転位に基づくピットが存在しており、その径も大きい。これに対して、窒化物半導体層（バッファー層）の表面では、図３（ｂ）に示すように、１点鎖線の丸で囲んだ広い箇所に少しのピットが存在するだけで、その径も小さくなっている。 As shown in FIG. 3A, on the surface of the ud-GaN layer, pits based on dislocations exist at many points circled, and their diameters are also large. On the other hand, on the surface of the nitride semiconductor layer (buffer layer), as shown in FIG. 3 (b), there are only a few pits in a wide area circled by the alternate long and short dash line, and the diameter is also large. It's getting smaller.
この結果より、上記と同様に、本実施の形態によれば、窒化物半導体基板において転位密度を低減できることが確認できる。なお、ピットの径が小さくなった理由としては、ＧａＮ層において形成されるピットの径はその成長温度と関係しており、上層となるＥｕ添加ＧａＮ層の成長を９６０℃という低温で行ったことにより、ピットの径が小さくなったためと考えられる。そして、ピットの径が小さくなってピットが塞がれると、転位密度がさらに低減される。 From this result, it can be confirmed that the dislocation density can be reduced in the nitride semiconductor substrate according to the present embodiment in the same manner as described above. The reason why the diameter of the pits became smaller is that the diameter of the pits formed in the GaN layer is related to the growth temperature, and the growth of the Eu-added GaN layer as the upper layer was performed at a low temperature of 960 ° C. It is probable that the diameter of the pit became smaller due to this. When the diameter of the pit becomes smaller and the pit is closed, the dislocation density is further reduced.
具体的に転位密度を測定したところ、図３（ａ）では１０８〜１０９オーダーであったのに対して、図３（ｂ）では１０６オーダーまで低減されていた。The measured specific dislocation density, whereas was 10 108 to 109 order in FIG. 3 (a), it had been reduced to 10 6 Order in FIG 3 (b).
（３）Ｅｕ添加ＧａＮ層の厚みと転位密度との関係
本発明者は、さらに、Ｅｕ添加ＧａＮ層の厚みと転位密度との関係について評価するために、上記と同様にして、厚み１０ｎｍのｕｄ−ＧａＮ層上に、Ｅｕ添加ＧａＮ層を厚み９００ｎｍまで成長させ、厚みが転位密度にどのように影響するのか評価した。(3) Relationship between the thickness of the Eu-added GaN layer and the dislocation density The present inventor further evaluates the relationship between the thickness of the Eu-added GaN layer and the dislocation density in the same manner as above. An Eu-added GaN layer was grown on the −GaN layer to a thickness of 900 nm, and how the thickness affects the dislocation density was evaluated.
具体的には、Ｅｕ添加ＧａＮ層の厚みが１００ｎｍ、３００ｎｍ、９００ｎｍとなった時点で、上記と同様に、表面に現われた転位の様子をＡＦＭにより観察した。 Specifically, when the thickness of the Eu-added GaN layer was 100 nm, 300 nm, and 900 nm, the state of dislocations appearing on the surface was observed by AFM in the same manner as described above.
図４は、それぞれの厚みのＥｕ添加ＧａＮ層の表面のＡＦＭ画像であり、（ａ）は厚み１００ｎｍ、（ｂ）は厚み３００ｎｍ、（ｃ）は厚み９００ｎｍにおける結果である。 FIG. 4 is an AFM image of the surface of the Eu-added GaN layer of each thickness, where (a) is a thickness of 100 nm, (b) is a thickness of 300 nm, and (c) is a result of a thickness of 900 nm.
図４より、Ｅｕ添加ＧａＮ層の厚みが増すにつれて、１点鎖線の丸で囲んで示すように、ピットが減少しており、厚み９００ｎｍでは殆ど消失していることが分かる。 From FIG. 4, it can be seen that as the thickness of the Eu-added GaN layer increases, the pits decrease as shown by circled by the alternate long and short dash line, and almost disappear at a thickness of 900 nm.
具体的に転位密度を測定したところ、図４（ａ）では１０８オーダー、図４（ｂ）では１０７オーダー、図４（ｃ）では１０６オーダーであり、厚みが増すにつれて、劇的に転位密度が低下することが確認できた。The measured specific dislocation density, FIGS. 4 (a) in 108 order, and FIG. 4 (b) in 107 order, a 106 order in FIG. 4 (c), the as the thickness increases dramatically It was confirmed that the dislocation density decreased.
（４）本実施の形態における転位密度の伝播
ここで、本実施の形態における転位密度の伝播について、図５を用いて説明する。なお、図５は、上記で作製された窒化物半導体基板の断面を特定の方向、具体的には、上向きｇ＝［００２］およびｇ＝［１１０］方向から観察したＴＥＭ画像であり、それぞれを上下に配置して示している。(4) Propagation of dislocation density in the present embodiment Here, the propagation of the dislocation density in the present embodiment will be described with reference to FIG. Note that FIG. 5 is a TEM image obtained by observing the cross section of the nitride semiconductor substrate produced above from a specific direction, specifically, upward g = [002] and g = [110] directions. It is shown by arranging it vertically.
図５において、ｇ＝［００２］方向はらせん転位（Ｓｃｒｅｗ ｄｉｓｌｏｃａｔｉｏｎ）を決定する方向であり、ｇ＝［１１０］方向は刃状転位（ｅｄｇｅ ｄｉｓｌｏｃａｔｉｏｎ）を決定する方向である。しかし、図５から分かるように、これらの転位の他に、ｇ＝［００２］方向およびｇ＝［１１０］方向の双方に、いくつかの転移が混合転位（Ｍｉｘ ｄｉｓｌｏｃａｔｉｏｎ）として現れており、これらの混合転位は窒化物半導体層（バッファー層）によって、その成長、消滅が支配されている。 In FIG. 5, the g = [002] direction is the direction for determining the screw dislocation, and the g = [110] direction is the direction for determining the edge dislocation. However, as can be seen from FIG. 5, in addition to these dislocations, some dislocations appear as mixed dislocations (Mix dislocation) in both the g = [002] direction and the g = [110] direction. The growth and disappearance of the mixed dislocations are controlled by the nitride semiconductor layer (buffer layer).
具体的に、図５では、混合転位が窒化物半導体層（バッファー層）のＥｕ添加ＧａＮ層に伝播した際、まず、らせん転位が収束されて消滅し、その後、刃状転位のベクトル（ｅｄｇｅ ｖｅｃｔｏｒ）が収束されて、１点鎖線の白抜き楕円で囲まれた箇所においては、２つの混合転位が表面まで到達することなく消滅している。 Specifically, in FIG. 5, when the mixed dislocations propagate to the Eu-added GaN layer of the nitride semiconductor layer (buffer layer), the spiral dislocations first converge and disappear, and then the edge vector (edge vector). ) Is converged, and the two mixed dislocations disappear without reaching the surface at the part surrounded by the white ellipse of the one-point chain line.
４．本実施の形態における効果
以上のように、本実施に形態においては、安価なサファイア基材上に、ｕｄ−ＧａＮ層とＥｕ添加ＧａＮ層を適切な厚みで１回積層するという簡便な方法で、１０６ｃｍ−２オーダー以下という十分に低転位密度の窒化物半導体基板を得ることができるため、高性能、長寿命の半導体デバイスを安価に提供するという近年の要請に好適に応えることができる。4. Effects in the present embodiment As described above, in the present embodiment, the ud-GaN layer and the Eu-added GaN layer are laminated once with an appropriate thickness on an inexpensive sapphire base material by a simple method. Since a nitride semiconductor substrate having a sufficiently low dislocation density of 10 6 cm- 2 orders or less can be obtained, it is possible to suitably meet the recent demand for inexpensively providing a high-performance, long-life semiconductor device.
［２］第２の実施の形態
上記した第１の実施の形態においては、ｕｄ−ＧａＮ層の上に積層されるＥｕ添加ＧａＮ層の厚みの増加に合わせて転位密度を低減させることができるが、Ｅｕ添加ＧａＮ層が厚くなり過ぎると、基材であるサファイアと窒化物半導体層のＧａＮとでは熱膨張係数に差があるためサファイアと窒化物半導体層との界面に反りが発生して、窒化物半導体基板として使用できなくなる恐れがある。[2] Second Embodiment In the first embodiment described above, the dislocation density can be reduced as the thickness of the Eu-added GaN layer laminated on the ud-GaN layer increases. If the Eu-added GaN layer becomes too thick, the sapphire as the base material and the GaN of the nitride semiconductor layer have different thermal expansion coefficients, so that the interface between the sapphire and the nitride semiconductor layer is warped and nitrided. There is a risk that it cannot be used as a physical semiconductor substrate.
そこで、本実施の形態においては、サファイア基材上にｕｄ−ＧａＮ層とＥｕ添加ＧａＮ層とを交互に積層することを複数回繰り返して、ｕｄ−ＧａＮ層とＥｕ添加ＧａＮ層の複数ペアを積層して超格子構造の窒化物半導体層を形成することにより、薄くても十分に転位密度が低減された窒化物半導体基板を製造している。 Therefore, in the present embodiment, the ud-GaN layer and the Eu-added GaN layer are alternately laminated on the sapphire substrate a plurality of times, and a plurality of pairs of the ud-GaN layer and the Eu-added GaN layer are laminated. By forming a nitride semiconductor layer having a superlattice structure, a nitride semiconductor substrate having a sufficiently reduced dislocation density even if it is thin is manufactured.
１．窒化物半導体基板の基本的な構成
最初に本実施の形態に係る窒化物半導体基板の基本的な構成について説明する。図６は、本実施の形態に係る窒化物半導体基板の構成を示す模式図である。なお、図６における符号は窒化物半導体基板が２である以外は図１と同様である。図６より分かるように、本実施の形態においては、窒化物半導体層２０が、Ｅｕ添加ＧａＮ層２２とｕｄ−ＧａＮ層２１を交互に複数回積層されており、また、Ｅｕ添加ＧａＮ層２２の酸化を抑制するという観点から最表層にｕｄ−ＧａＮ層２１が形成されている点を除いては、第１の実施の形態に係る窒化物半導体基板と同様の構成となっている。1. 1. Basic Configuration of Nitride Semiconductor Substrate First, the basic configuration of the nitride semiconductor substrate according to the present embodiment will be described. FIG. 6 is a schematic view showing the configuration of the nitride semiconductor substrate according to the present embodiment. The reference numerals in FIG. 6 are the same as those in FIG. 1 except that the nitride semiconductor substrate is 2. As can be seen from FIG. 6, in the present embodiment, the
２．窒化物半導体基板の製造方法
そして、本実施の形態に係る窒化物半導体基板２の製造方法についても、ｕｄ−ＧａＮ層２１とＥｕ添加ＧａＮ層２２の形成を繰り返しながら行って、ｕｄ−ＧａＮ層２１とＥｕ添加ＧａＮ層２２の複数ペアを積層することを除いては、第１の実施の形態に係る窒化物半導体基板の製造方法と同様である。なお、本実施の形態においても、各層の形成は、途中で試料を反応管より取り出すことなく、成長の中断がないように一連の工程で行った。2. Method for Manufacturing Nitride Semiconductor Substrate The method for manufacturing the
３．転位密度の評価
（１）ＡＦＭ画像に基づく評価
上記した窒化物半導体基板の製造方法を用い、厚み１０ｎｍのｕｄ−ＧａＮ層２１および厚み１ｎｍのＥｕ添加ＧａＮ層２２を、交互に４０回（４０ペア）積層して作製された窒化物半導体基板２の転位密度について、第１の実施の形態と同様に、ＡＦＭ画像に基づいて転位密度の低減効果を評価した。3. 3. Evaluation of dislocation density (1) Evaluation based on AFM image Using the above-mentioned method for manufacturing a nitride semiconductor substrate, the ud-
図７は窒化物半導体基板の表面のＡＦＭ画像である。この図７と、厚み９００ｎｍのＥｕ添加ＧａＮ層を１回積層した窒化物半導体基板の表面のＡＦＭ画像である図４（ｃ）とを比較すると、総厚４８０ｎｍ（最表層のｕｄ−ＧａＮ層を含む）と図４（ｃ）に比べて約半分の厚みでありながらも、さらに、転位密度が低下していることが分かる。 FIG. 7 is an AFM image of the surface of the nitride semiconductor substrate. Comparing this FIG. 7 with FIG. 4 (c), which is an AFM image of the surface of a nitride semiconductor substrate in which an Eu-added GaN layer having a thickness of 900 nm is laminated once, a ud-GaN layer having a total thickness of 480 nm (the outermost layer) is obtained. It can be seen that the dislocation density is further reduced, although the thickness is about half that of FIG. 4 (c).
この結果より、本実施の形態によれば、複数回積層して超格子構造の窒化物半導体層としたことにより、それぞれのＥｕ添加ＧａＮ層において転位が曲げられて、薄い総厚であっても劇的に転位密度を低下できることが確認できた。 From this result, according to the present embodiment, by laminating a plurality of times to form a nitride semiconductor layer having a superlattice structure, dislocations are bent in each Eu-added GaN layer, and even if the total thickness is thin. It was confirmed that the dislocation density can be dramatically reduced.
（２）ペア数（積層回数）の転位密度低減への影響
次に、ペア数（積層回数）の転位密度低減への影響を調べるために、上記した窒化物半導体基板の製造方法を用い、厚み１０ｎｍのｕｄ−ＧａＮ層２１および厚み３ｎｍのＥｕ添加ＧａＮ層２２を交互に積層して、ペア数（積層回数）を１３（実験Ａ）、４０（実験Ｂ）、７０（実験Ｃ）と変えた３種類の窒化物半導体層が形成された窒化物半導体基板２について、それぞれ転位密度を測定した。(2) Effect of number of pairs (number of stacks) on reduction of dislocation density Next, in order to investigate the effect of number of pairs (number of stacks) on reduction of dislocation density, the above-mentioned method for manufacturing a nitride semiconductor substrate was used to obtain thickness. The 10 nm ud-
測定結果を表１に示すと共に、図８に示す。なお、図８において横軸はペア数、縦軸は転位密度（×１０６ｃｍ−２）である。また、実験Ｂにおいて４０ペア積層して作製された窒化物半導体基板の断面ＴＥＭ像を図９に示す。The measurement results are shown in Table 1 and FIG. The horizontal axis represents the number of pairs in FIG. 8, a vertical axis represents the dislocation density (× 10 6 cm -2). Further, FIG. 9 shows a cross-sectional TEM image of the nitride semiconductor substrate produced by laminating 40 pairs in Experiment B.
表１および図７より、最もペア数の少ない１３ペアでも転位密度は１０６ｃｍ−２オーダーであり、ペア数が多くなるにつれて転位密度が低下することが分かる。From Table 1 and Figure 7, the most dislocation density in pairs having a small number of 13 pairs is 10 6 cm -2 order, it can be seen that the dislocation density decreases as the number of pairs increases.
そして、図９では、Ｄｉｓｌｏｃａｔｉｏｎ１とＤｉｓｌｏｃａｔｉｏｎ２、２つの転位が存在しているが、Ｄｉｓｌｏｃａｔｉｏｎ１では、窒化物半導体層（バッファー層）内に入った後、収束されて消滅している。一方、Ｄｉｓｌｏｃａｔｉｏｎ２では、消滅はしていないものの、ペアを通過するにつれて転位のサイズが小さくなっている。この結果から見ても、表１および図７において、７０ペアとさらにペア数を増やした実験Ｃにおいて、さらに、転位密度が低下していることが理解できる。
Then, in FIG. 9, two dislocations,
そして、上記の結果は、青色レーザによるピックアップやＳｉやＳｉＣ等を用いた縦型パワートランジスタを作製する場合に必要とされる転位密度（１０６ｃｍ−２オーダー）を満たしているため、本実施の形態に係る窒化物半導体基板は、サファイア基材上に形成されているにも拘らず、Ｂｌｕ−Ｒａｙに用いられるピックアップ用青色レーザおよび縦型パワートランジスタの製造に使用できることが分かる。The above results, because they meet the dislocation density (10 6 cm -2 order) required in the case of manufacturing a vertical power transistor using a pickup or Si and SiC or the like by the blue laser, this embodiment It can be seen that the nitride semiconductor substrate according to the above embodiment can be used for manufacturing a blue laser for pickup and a vertical power transistor used for Blu-Ray, although it is formed on a sapphire substrate.
また、ペア数が多くなるに従い転位密度が低減されるため、さらにペア数を増やしてさらに転位密度を低減させることにより、Ｂｌｕ−Ｒａｙに用いられる書き込み用の青色レーザに必要とされている１０４ｃｍ−２オーダーが達成できることが期待される。Further, since the dislocation density is reduced as the number of pairs increases, by reducing the further dislocation density further increase the number of pairs, 10 4 that is required for a blue laser for writing to be used in the Blu-Ray It is expected that the cm- 2 order can be achieved.
以上、本発明によれば、第１の実施の形態および第２の実施の形態に示したように、安価なサファイア基材等を用いて、高品質の窒化物半導体の製造を可能とする窒化物半導体基板を提供することができる。また、窒化物層を基材全面に形成することが可能なため、大面積化が可能であり実用性に優れる。 As described above, according to the present invention, as shown in the first embodiment and the second embodiment, nitridation that enables the production of high-quality nitride semiconductors by using an inexpensive sapphire substrate or the like. A physical semiconductor substrate can be provided. Further, since the nitride layer can be formed on the entire surface of the base material, the area can be increased and the practicality is excellent.
そして、上記の窒化物半導体基板から基材を除去することにより、窒化物半導体バルク基板とすることもできるため、半導体デバイス用の窒化物半導体基板として、さらに利用が広がる可能性がある。 Then, by removing the base material from the above-mentioned nitride semiconductor substrate, a nitride semiconductor bulk substrate can be obtained, so that the use as a nitride semiconductor substrate for semiconductor devices may be further expanded.
以上、本発明を実施の形態に基づき説明したが、本発明は上記の実施の形態に限定されるものではない。本発明と同一および均等の範囲内において、上記の実施の形態に対して種々の変更を加えることが可能である。 Although the present invention has been described above based on the embodiments, the present invention is not limited to the above embodiments. Within the same and equal scope as the present invention, various modifications can be made to the above embodiments.
１、２ 窒化物半導体基板
１０ サファイア基材
２０ 窒化物半導体層（バッファー層）
２１ ｕｄ−ＧａＮ層
２２ Ｅｕ添加ＧａＮ層
３０ ＬＴ−ＧａＮ層
４０ ｕｄ−ＧａＮ層1, 2
21 ud-
Claims (20)
前記窒化物半導体層が、
ドーピング材料が添加されていない厚みが窒化物結晶の格子定数以上で５０ｎｍ以下のアンドープ窒化物層と、
ドーピング材料として希土類元素が添加された厚みが窒化物結晶の格子定数以上で２０００ｎｍ以下の希土類元素添加窒化物層とが１回積層されて形成されており、
前記窒化物半導体層の表面における転位密度が１０６ｃｍ−２オーダー以下であることを特徴とする窒化物半導体基板。 A nitride semiconductor substrate in which a nitride semiconductor layer is formed on a base material.
The nitride semiconductor layer
An undoped nitride layer having a thickness of 50 nm or less, which is equal to or greater than the lattice constant of the nitride crystal, to which no doping material is added.
A rare earth element-added nitride layer having a thickness of 2000 nm or less, which is equal to or more than the lattice constant of the nitride crystal, is laminated once as a doping material.
Nitride semiconductor substrate, wherein the dislocation density on the surface of the nitride semiconductor layer is not more than 10 6 cm -2 order.
前記窒化物半導体層が、
ドーピング材料が添加されていない厚みが窒化物結晶の格子定数以上で５０ｎｍ以下のアンドープ窒化物層と、
ドーピング材料として希土類元素が添加された厚みが窒化物結晶の格子定数以上で２００ｎｍ以下の希土類元素添加窒化物層とが複数回積層されて超格子構造に形成されており、
前記窒化物半導体層の表面における転位密度が１０６ｃｍ−２オーダー以下であることを特徴とする窒化物半導体基板。 A nitride semiconductor substrate in which a nitride semiconductor layer is formed on a base material.
The nitride semiconductor layer
An undoped nitride layer having a thickness of 50 nm or less, which is equal to or greater than the lattice constant of the nitride crystal, to which no doping material is added.
A superlattice structure is formed by laminating a rare earth element-added nitride layer having a thickness of 200 nm or less, which is equal to or more than the lattice constant of the nitride crystal, to which a rare earth element has been added as a doping material multiple times.
Nitride semiconductor substrate, wherein the dislocation density on the surface of the nitride semiconductor layer is not more than 10 6 cm -2 order.
前記窒化物半導体層が、局所的な歪が異なる厚みが窒化物結晶の格子定数以上で５０ｎｍ以下のアンドープ窒化物層および厚みが窒化物結晶の格子定数以上で２０００ｎｍ以下の希土類元素添加窒化物層が交互に１回積層された構造を有しており、
前記窒化物半導体層の表面における転位密度が１０６ｃｍ−２オーダー以下であることを特徴とする窒化物半導体基板。 A nitride semiconductor substrate in which a nitride semiconductor layer is formed on a base material.
The nitride semiconductor layer has an undoped nitride layer having a thickness different from the lattice constant of the nitride crystal and having a thickness of 50 nm or less, and a rare earth element-added nitride layer having a thickness of 2000 nm or less having a lattice constant of the nitride crystal or more. Has a structure in which is alternately laminated once.
Nitride semiconductor substrate, wherein the dislocation density on the surface of the nitride semiconductor layer is not more than 10 6 cm -2 order.
前記窒化物半導体層が、局所的な歪が異なる厚みが窒化物結晶の格子定数以上で５０ｎｍ以下のアンドープ窒化物層および厚みが窒化物結晶の格子定数以上で２００ｎｍ以下の希土類元素添加窒化物層が交互に複数回積層された超格子構造を有しており、
前記窒化物半導体層の表面における転位密度が１０６ｃｍ−２オーダー以下であることを特徴とする窒化物半導体基板。 A nitride semiconductor substrate in which a nitride semiconductor layer is formed on a base material.
The nitride semiconductor layer has an undoped nitride layer having a thickness different from that of the nitride crystal and having a thickness of 50 nm or more and a lattice constant of a nitride crystal having a thickness of 200 nm or less. Has a superlattice structure in which is alternately laminated multiple times.
Nitride semiconductor substrate, wherein the dislocation density on the surface of the nitride semiconductor layer is not more than 10 6 cm -2 order.
基材上にＧａＮ、ＩｎＮ、ＡｌＮ、またはこれらのいずれか２つ以上の混晶を成長させて、ドーピング材料が添加されていないアンドープ窒化物層を窒化物結晶の格子定数以上で５０ｎｍ以下の厚みに形成する工程と、
前記アンドープ窒化物層の上に、ＧａＮ、ＩｎＮ、ＡｌＮ、またはこれらのいずれか２つ以上の混晶を母体材料とし、ドーピング材料として希土類元素をＧａ、ＩｎあるいはＡｌと置換するように添加することにより、希土類元素添加窒化物層を窒化物結晶の格子定数以上で２０００ｎｍ以下の厚みに形成する工程とを備えており、
前記２つの工程を、有機金属気相エピタキシャル法を用いて、９００〜１２００℃の温度条件の下で、反応容器から取り出すことなく一連の形成工程によって行うことを特徴とする窒化物半導体基板の製造方法。 A method for manufacturing a nitride semiconductor substrate in which a nitride semiconductor layer is formed on a base material.
GaN, InN, AlN, or a mixed crystal of any two or more of these is grown on the substrate, and the undoped nitride layer to which no doping material is added has a thickness of 50 nm or less at the lattice constant of the nitride crystal or more. And the process of forming
On the undoped nitride layer, GaN, InN, AlN, or a mixed crystal of any two or more of these is used as a base material, and a rare earth element is added as a doping material so as to replace Ga, In, or Al. This includes a step of forming the rare earth element-added nitride layer to a thickness of 2000 nm or less, which is equal to or more than the lattice constant of the nitride crystal.
Manufacture of a nitride semiconductor substrate, wherein the two steps are carried out by a series of forming steps using an organic metal vapor phase epitaxial method under a temperature condition of 900 to 1200 ° C. without taking out from the reaction vessel. Method.
基材上にＧａＮ、ＩｎＮ、ＡｌＮ、またはこれらのいずれか２つ以上の混晶を成長させて、ドーピング材料が添加されていないアンドープ窒化物層を形成する工程と、
前記アンドープ窒化物層の上に、ＧａＮ、ＩｎＮ、ＡｌＮ、またはこれらのいずれか２つ以上の混晶を母体材料とし、ドーピング材料として希土類元素をＧａ、ＩｎあるいはＡｌと置換するように添加することにより、希土類元素添加窒化物層を窒化物結晶の格子定数以上で２００ｎｍ以下の厚みに形成する工程とを備えており、
前記２つの工程を、有機金属気相エピタキシャル法を用いて、９００〜１２００℃の温度条件の下で、反応容器から取り出すことなく一連の形成工程によって、交互に、複数回繰り返し行うことを特徴とする窒化物半導体基板の製造方法。 A method for manufacturing a nitride semiconductor substrate in which a nitride semiconductor layer is formed on a base material.
A step of growing GaN, InN, AlN, or a mixed crystal of any two or more of these on a substrate to form an undoped nitride layer to which no doping material is added.
On the undoped nitride layer, GaN, InN, AlN, or a mixed crystal of any two or more of these is used as a base material, and a rare earth element is added as a doping material so as to replace Ga, In, or Al. This comprises a step of forming the rare earth element-added nitride layer to a thickness of 200 nm or less, which is equal to or greater than the lattice constant of the nitride crystal.
The feature is that the above two steps are alternately repeated a plurality of times by a series of forming steps using an organic metal vapor phase epitaxial method under a temperature condition of 900 to 1200 ° C. without taking out from the reaction vessel. A method for manufacturing a nitride semiconductor substrate.
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| US9048100B2 (en) | 2007-11-21 | 2015-06-02 | Mitsubishi Chemical Corporation | Nitride semiconductor and nitride semiconductor crystal growth method |
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| JP5380754B2 (en) | 2010-02-12 | 2014-01-08 | 日立金属株式会社 | Method for manufacturing nitride semiconductor free-standing substrate and method for manufacturing nitride semiconductor device |
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